EMF Compliance and Enforcement


On 17 June 2021, Ofcom published updated and simplified guidance on the new electromagnetic field (EMF) licence condition and what you need to know as a ships radio licensee.

All transmitting radio equipment emits EMF, the purpose of the new condition is to protect members of “the public” from harmful EMF emissions and it applies to all marine communications and associated electronics such as radio, radar and other equipment on a vessel and in shore-based installations such as yacht clubs.

Ofcom includes family and friends as members of “the public” (see Section 4 of the Guidance on EMF Compliance and Enforcement document). The owner, skipper, and any paid crew of the vessel are excluded but, if you are carrying family and friends on board even as crew you will need to comply.

Ofcom has also published an updated and simplified version of its EMF calculator.

RYA guidance on compliance

License holders are required to provide evidence that their equipment does not exceed the EMF limits. However, if any of the following apply, no further action is required:

1. You do not transmit at power levels higher 6.1 Watts Effective Radiated Power (ERP). This means that you do not need to take any further action for any of the following:

AIS Class A and Class B transceivers
MOB devices 
Handheld VHF Radio with or without DSC 
Radar Target Enhancers
AIS SART and SART (Search And Rescue Transponder)
Handheld satellite phones

2. Your licence does not permit you to transmit at power levels higher than 6.1 Watts ERP.

3. You only use your radio equipment in an emergency (see Section 13 of the Guidance on EMF Compliance and Enforcement document).

Otherwise, you should carry out a compliance check to ensure the antenna is far enough away from the general public when you are transmitting. You can do this by:

1. Installing the equipment in accordance with the manufacturer’s instructions on EMF compliance. Keep a copy of the equipment manufacturer’s instructions on board the vessel. If they have been lost, they may be available and can be printed from the internet. If the equipment has been installed by a radiocommunications industry professional, ask the installer to provide appropriate EMF compliance records to be kept on board.

2. If the manufacturer’s instructions cannot be located, use the EMF calculator. The calculator will calculate the safe separation distance from the antenna. You should keep a copy of this calculation onboard.

Using the EMF Calculator

The calculator is very basic, however, whilst it is simple to use, it does use some technical terminology that goes way beyond the knowledge of the average marine radio operator.

ERP (Effective Radiated Power): ERP is the transmitting power of your equipment at the antenna. The Maximum ERP for a handheld VHF radio is 5w and 25W for a fixed VHF radio. For Radar this is in the order of 20W.

EIRP (Effective Isotropic Radiated Power): EIRP is calculated by multiplying the equipment’s ERP by a factor of 1.64. The EMF calculator lets you choose ERP or EIRP as an input parameter.

Operating frequency: frequency in MHz that the equipment is transmitting, for example a VHF marine band radio transmits on 156MHz, X band radar operates between 8000MHz - 12000MHz

Maximum transmission time: this is used to calculate the average radiated power in a six-minute period. For example, if you usually transmit short messages of up to ten seconds but do this is up to e.g. six times in a busy six-minute period, you should use a maximum transmission time of 1 minute (6 x 10 seconds)

When you input ERP/EIRP, maximum transmission time and operating frequency, the calculator will determine the separation distance to be maintained between the antenna and the public.

User manuals should provide details of transmitting power and operating frequency. You decide the maximum transmission time. If you still cannot find out what the ERP is you can use the power calculation tab in the EMF Calculator.

Here are some examples:


A VHF radio transmitting on 156MHz at 25watts ERP for 100% of the time would require a separation distance of 2.04m.

If you know that the radio will not transmit continuously, you can take this into account in the calculator. For example, if you know that the radio will not be used for more than 50 % of the time in a 6 minute period, you can enter this into the calculator instead which gives a separation distance of 1.45m. In reality, you will probably be transmitting far less than this.

As most VHF transmissions are transmitted at 1 Watt, the safe separation distance from the antenna is easily achieved, however, it is recommended that you keep a note of the safe separation distance for transmissions at 25 watts.


Similar calculations should be conducted for radar. Most marine installations will be operating on X band in the 9GHx to 12GHz range, 1GHz = 1000MHz

A marine radar transmitting all the time on 9000MHz at 20 watts ERP would require a separation distance of 0.64m.

As can be seen from the examples above, compliance is easily achievable.

Time period for compliance

Licensees that have had their licence(s) varied to include the new EMF condition, have the following time periods to ensure that EMF compliance records for all their radio equipment that is subject to the EMF condition are in place and up to date:

1. Until 18 November 2021 for any equipment which operates at frequencies above 110MHz.

2. Until 18 May 2022 for any equipment such as MF/HF sets which operates at frequencies between 10 and 110MHz inclusive.

3. Until 18 November 2022 for any equipment which operates at frequencies below 10MHz.